Glucagon and Insulin Release: Influence of Drugs Affecting the Autonomic Nervous System

Abstract

Isolated rat islets of Langerhans were used to study the direct effect of autonomic nervous system compounds on immunoreactive glucagon (IRG) and insulin (IRI) release. None of the substances affected IRG release. Epinephrine (10μ.M) and norepinephrine (10μM) blocked IRI release in response to 150 mg./100 ml. glucose but did not block the effect of 300 mg./100 ml. glucose. Acetylcholine (3 μM) stimulated IRI release but isoproterenol had no effect. Because the adenylcyclase system may play a role in adrenergic receptor mechanisms, the effects of substances which alter cellular levels of cyclic AMP were also studied. Again, none of the compounds altered IRG levels in the incubation media. Aminophylline (100 μM) stimulated IRI release but dibutyryl cyclic AMP and prostaglandin Ex were without significant effect. The results suggested that neither autonomc nervous sys tem compounds or the adenylcyclase system directly affect IRG release. The physiolugical significance of the direct inhibitory effect of substances with alpha adrenergic properties on IRI release is questioned in view of the very high concentration required for effect.